Aqueous bleaching solutions of peroxycarboxylic acids



United States Patent 3,248,336 AQUEOUS BLEACHING SOLUTIONS OFPEROXYCARBOXYLIC ACIDS John H. Blumhergs, Highland Park, NJ., assignorto FMC Corporation, New York, N.Y., a corporation of Delaware NoDrawing. Filed Apr. 6, 1964, Ser. No. 357,765

5 Claims. (Cl. 252-186) The present invention relates to a process forproducing'stable, aqueous solutionsof peroxybenzoic acid and substitutedperoxybenzoic acids for use as bleaching agents. 1

This is in a continuation-in-part of application Serial No. 119,325, now-U.S. Patent 3,130,169, filed on June 26, 1961, in the name of John H.Blumbergs et al. I

In the process of laundering textile garments in domestic washingmachines, it is common to employ a bleaching agent in addition to adetergent to maintain the original whiteness of the garments afterlaundering.

It is preferred to add the bleach in the form of a dilute, aqueoussolution to avoid localized bleach-ing and for ease in measuring andadding the varied amounts of bleach required with different garments anddifferent Washing loads.

Bleaching agents presently in use have been found to have seriousdrawbacks. For example, sodium hypochlorite, a commonly used bleach, hasthe disadvantage of not being stable in aqueous solutions and losing itseffective bleaching power on storage. In addition, it causes measurabledegradation of the fabric during bleaching and is capable of causinglocalized oven-bleaching by direct contact of the bleach with the fabricin the absence of water. Other active chlorine bleaching agents, such asthe chlorinated isocyanuric acids, are

more stable than sodium hypochlorite but these too can cause measurabledegradation of the fabric and are subject to localized olverbleaching.

Other types of bleaches have been suggested to overcome the problem offabric degradation, e.g. sodium perborate and potassium persulfates(Caroates). In the case of sodium perborate, fabric degradation isreducd but the bleaching action is inferior to the prior sodiumhypochlorite bleaches when conducted under conventional domestic Washingconditions. Similarly, the potassium persulfate bleaches give improvedbleaching action over sodium persulfate but are inferior to sodiumhypochlorite. "Further, potassium persulfates are not stable in aqueoussolutions, and therefore, cannot be supplied in the form of dilute,aqueous bleaching solutions.

Peroxybenzoic acid and substituted peroxybenzoic acids give goodbleaching action and do not degrade the bleached fabric but they havenot been used as domestic laundry bleaching agents because of the poorstability of these compositions in solution and the inability to formstable, aqueous-based solutions thereof.

' In US. Patent 3,075,921, issued on January 29, 1963,

to Peter Brocklehurst et al., there is described a process for making adry detergent composition containing as a bleaching agent, selected,substituted peroxybenzoic acids which are more stable than peroxybenzoicacid per se. The substituted peroxybenzoic acids are present asdiscrete, dry solids in the dry detergent composition;

no provision is taught for preparing aqueous based, clear I bleachingsolutions of. these peroxy acids for easy addition in domestic washingmachines. As a result, there has been a need for an eifective bleachingagent which can be supplied as a stable, aqueous solution and which doesnot degrade the fabric during bleach-ing.

It is an object of the present invention to provide a stable, aqueoussolution of a bleaching agent which is 3,248,336 Patented Apr. 26, 1966effective in giving a high degree of brightness without degrading thefabric during bleaching.

I have now found that peroxybenzoic acid and substituted peroxybenzoicacids which do not contain oxidizable groups can be made up into stable,aqueous-based bleaching solutions by dissolving these acids in a mixedsolvent comprising water and tert-butyl alcohol, in which the tert-butylalcohol is present in a weight ratio relative to the water of up to 1:1,but always in amounts sufficient to both dissolve and stabilize theperoxy acid and to form a homogeneous solution.

It is most unexpected to find that tert-butyl alcohol can be used tomake up stable, homogeneous, aqueous solutions of these non-oxidizableperoxybenzoic acids, particularly since these peroxy acids alone arevirtually insoluble in water. In my parent application U.S. Serial No.119,325, filed on June 26, 1961, I have taught that certain tertiaryalcohol solvents are capable of stabilizing peroxycarboxylic acids. Inthat application, the tertiary alcohol was used either alone as theentire solvent or mixed with small amounts (no more than 20% by weight.)of another organic solvent for the peroxycarboxylic acid. In the presentapplication, as little as 10% by Weight of the tertiary alcohol in awater solution has been found elfective in stabilizing theperoxycarboxylic acid.

The only tertiary alcohol useful in the present invention is tert-butylalcohol. Other tertiary alcohols, which are sparingly soluble in water,have not been found effective in making up the present homogeneous,aqueous bleaching solutions. The tert-butyl alcohol can be used to makeup the aqueous-based solutions of the peroxybenzoic acids up to about12% by weight when the alcohol is present in a 1:1 weight ratio withwater. Lower amounts of the tert-butyl alcohol can be used to make upmore dilute peroxy acid solutions. A dilute solution of about 2% byweight peroxy acid requires about 10% by weight of the tertiary alcoholsto impart stability and homogeneity to the aqueous solution.

The tertiary alcohols used in making up the aqueous bleach solutionshould be free of impurities that can cause rapid decompositon of theperoxybenzoic acids or which can be oxidized by these acids, thuswastefully consuming them. The most common offending impurities areheavy metals. Heavy metals initiate catalytic decomposition of theperoxybenzoic acids, and therefore, are highly undesirable, even insmall amounts.

Two methods can be employed to eliminate decomposition by heavy metals.The first of these is to remove the heavy metals by distilling thetertiary alcohols in glass or glass-lined equipment. Another is torender the heavy metals inactive by adding a small amount, on the orderof about p.p.m., of a metal chelating agent. A compound such asdip-icolinic acid is an ideal chelating agent and effectively ties upthe heavy metal in a complex organic structure, thereby making itunavailable for initiating decomposition of the peroxybenzoic acids.

The peroxy acid which has been found most suitable in the presentbleaching solution is peroxybenzoic acid because of its high solubilityin the tert-butyl alcohol and because it has proportionately more activeoxygen per molecular weight than do the substituted peroxybenzoic acids.Aqueous solutions having up to about 12% by weight of peroxybenzoic acidcan be made up readily when tertbutyl alcohol is employed as thetertiary alcohol. In making up such solutions, they should contain about44% by weight water, about 12% by weight peroxybenzoic acid, and fromabout 44% by weight tertbutyl alcohol. A preferred bleaching mixturecontains from about 52% by weight water, about 9% peroxybenzoic acid,and 39% by weight of tert-butyl alcohol.

In addition to peroxybenzoic acid, substituted peroxybenzoic acids canbe employed which do not contain groups that can be oxidized by theperoxybenzoic acids.

p. 1061. The concentration of the ingredients in the solution and theresults of the analysis are listed in Table 1 below:

Table I Sample No.

Peracid and Hydrogen Peroxide Content Sample Composition At After AfterAfter Start 1 Month 3 Months 6 Months Storage Storage StoragePeroxybenzoic Acid, percent.

Hydrogen Peroxide, percent. Tert-butanol, percent- Distilled Water,percent Dipicolinic Acid, p.p.rn Peroxybenzoie Acid, percent--..Hydrogen Peroxide, percent. Tcrt-butanol, percent. Distilled Water,percent Dipicolinic Acid, p.p.m.

Hydrogen Peroxide, percent- Tcrt-butanol, percent. Distilled Water,percent Dipicolinic Acid, ppm.

These substituted peroxybenzoic acids further must be sufiicientlysoluble in the tertiary alcohol-water mixture to reach the peroxy acidcontent desired. For example, nitro groups are non-oxidizable, but theyare unsuitable in the present application because the nitro group solowers the solubility of the resultant peroxybenzoic acid that it cannotbe used in making up the present bleach solutions. Substitutedperoxybenzoic acids which contain chloro, lower saturated aliphatic,methoxy, and other such groups have been found suitable. Compounds suchas ortho-chloroperoxybenzoic acid, para-chloroperoxybenzoic acid,meta-chloroperoxybenzoic acid, para-tertiary butyl peroxybenzoic acid,and para-methoxy peroxybenzoic acid, have been found suitable. Examplesof substituents on the peroxybenzoic acid which are oxidizable, andtherefore unsuitable, include primary and secondary alcoholic groups,hydroxyl, ketonic and aldehydic groups.

In contrast to the present peroxybenzoic acids, the aliphaticperoxycarboxylic acids have not been found suitable in this applicationbecause they undesirably hydrolyze in aqueous solutions to thecorresponding acid and hydro gen peroxide. Peroxy-benzoic acid andsubstituted peroxybenzoic acids, in contrast, have negligible rates ofhydrolysis in water solutions and therefore, are effective in retainingtheir active oxygen contents for a sustained period in aqueoussolutions.

In addition to being excellent bleaching agents, the presentaqueous-based peroxybenzoic acid solutions have been found to have highgermicidal action. This is advantageous because the bleaching agenteffectively sterilizes the soiled garments it contacts duringconventional domestic laundering. In addition, if desired, the presentaqueous solutions can be used as germicidal and disinfecting solutionsbecause of their high germicidal action. The makeup of these germicidesin an aqueous base facilitates their use and permits sterilization ofequipment without residual organic solvents being retained thereon.

The following examples are given to illustrate the invention and are notdeemed to be limiting thereof.

EXAMPLE 1 Peroxybenzoic acid was dissolved in tert-butyl alcohol andthis solution was mixed with various proportions of distilled water. Tothese solutions were added small amounts of dipicolinic acid to act assequestering agents 10 for the removal of heavy metal ion impurities.The samples were stored at room temperature (about C.) for up to 6months and were analyzed periodically for their peroxy acid and hydrogenperoxide content by the method described in Analytical Chemistry, 20(1948),

{Peroxybenzoic Acid, percent Peroxybenzoic Acid, percent. 1. 40 1. 39 1.31 1. 22 Hydrogen Peroxide, percent- 0. 00 Trace Trace 0.02Tert-butanol, percent.- 9. 5 Distilled Water, percent 89. 1 DipicolinicAcid, p.p.m.......

In this example, the amount of hydrogen peroxide in the sample indicatesthe degree of hydrolysis of the peroxybenzoic acid in accordance withthe formula set forth below:

i i RCOOH H20 R-OOH H201 The greater the amount of hydrogen peroxide inthe solutions, the greater the hydrolysis and the less effective is thebleaching and germicidal activity of the peroxybenzoic acid solution.

EXAMPLE 2 The peroxybenzoic acid solution identified as Sample 1 inExample 1, after storage for 6 months at room temperature, and whichcontained 11.04% by weight of peroxybenzoic acid, was tested forgermicidal activity against Staphylococcus aureus by the standardprocedure for phenol coefficient determination as described in OfficialMethods of Analyses of the A.O.A.C., published by A.O.A.C. (1960), pp.63-65. The phenol coefficient was found to be 400, calculated on thebasis of the active ingredient. An acceptable, active germicide shouldhave a phenol coefficient of about 200.

EXAMPLE 3 The peroxybenzoic acid solution identified as Sample 1 inExample 1, after storage for 6 months at room temperature, and whichcontained 11.04% by weight of peroxybenzoic acid, was tested forbleaching effectiveness. The procedure used was as follows: Thirty-twocotton" swatches (5" x 5" desized cotton Indianhead fabric, uniform inweave and thread count) were stained with tea, coffee and wine in thefollowing manner: Five tea bags were placed in a liter of water andboiled for 5 minutes. Thereafter, the swatches were immersed in tea andthe boiling continued for 5 minutes. Thirty-two additional swatches ofthe same cloth were coffee-stained by boiling 50 g. of coffee in a literof water, immersing the swatches in the coffee solution and boiling foran additional 5 minutes. The wine stains were created by soakingswatches of the same cloth in a red wine at room temperature. Thestained swatches were then squeezed to remove excess fluid, dried,rinsed in cold water and dried. Three of the stained cotton swatcheswere then added to each of a series of stainless steel Terg-O-Tometervessels (produced by the [1.5. Testing Company) containing 1,000 ml. ofa 0.2% standard detergent solution at a temperature of F. Measuredamounts of the bleach solution were then added to each vessel sufiicientto correspond to an active oxygen content of 20, 40, 60 and 80 ppm.respectively. The pH of the solutions were adjusted to 9.5, using sodaash. Cut-up pieces of white terry cloth toweling were then added toprovide a typical household wash 'water/ cloth ratio of 20:1. TheTerg-O-Tometer was then operated at 72 cycles per minute for 15 minutesat a temperature of 120 F. At the end of the wash cycle, the swatcheswere removed, rinsed under cold tap water and dried in aProctor-Schwartz skeiu'dryer. The tests Were run in triplicate andincluded detergent blanks. Reflectance readings of the swatches werethen taken before and after the wash cycle wth a Reflectometer and thereadings were averaged. The percent stain removal was obtained inaccordance with the following formula:

Total percent stain removal:

Reflectance after bleaching- Reflectance before bleaching Reflectancebefore staining- Reflectance stained Meta-chloroperoxybenzoic'acid wasdissolved in tertbutyl alcohol and this solution was mixed with variousproportions of distilled Water. To these solutions were added smallamounts of dipicolinic acid to act as sequestering agents for theremoval of heavy metal ion impurities. The samples were stored at roomtemperature (about 25 C.) for up to 6 months and were analyzedperiodically for their peroxy acid and hydrogen peroxide content by themethod described in Analytical Chemistry, 20 (1948), p. 1061. Theconcentration of the ingredients in the solution and the results of theanalysis are listed in Table III below:

6 EXAMPLE 5 The solution identified as Samples 1 and 2 used in Example4, after storage for 6 months and having metachloroperoxybenzoic acidcontents of 9.80% and 9.95%

respectively, were each tested for germicidal activity in the same wayas described in Example 2. The phenol coefiicients of these samples aregiven in Table 1V and are calculated on the basis of the activeingredient.

Table IV Sample Tested Microorganisms Phenol Coefficient 1Staphylococcus aureus 383 2. .do I 400 EXAMPLE 6 The solution identifiedas Sample 1 in Example 4, after storage for 6 months at room temperatureand having a meta-chloroperoxybenzoic acid content of 9.80%, was testedfor its bleaching activity as set forth in Example 3. The results ofthese bleaching tests are given in Table V below:

Table V Sample Tested Active Percent Stain Removal (Sample 1 fromContents, Oxygen Table 3) Percent Content,

p.p.m. Tea Coffee Wme Meta-chloroperoxybenzoic acid 9. 80 20 61.5 89.385.4

Hydrogen Pcro 0.00 40 70.5 93.3 92.0 Tert-butanol 44.5 73.6 95.3 95.3Distilled Water 44.5 75.8 96.2 94.5 Dipicolinic Acid 1 Detergent Blank26.9 45.0 61 0 1 Parts per million.

Pursuant to the requirements of the patent statutes, the principle ofthis invention has been explained and exemplified in a manner so that itcan be readily practiced by those skilled in the art, suchexemplification including what is considered to represent the bestembodiment of the invention. However, it should be clearly understoodthat, within the scope of the appended claims, the invention may bepracticed by those skilled in the art, and having the benefit of thisdisclosure otherwise than as specifically described and exemplifiedherein.

What is claimed is: v

1. A stable, aqueous based composition which consists percent. HydrogenPeroxide, percent... Tert-butanol, percent. Distilled Water, percentDipicolinic Acid, p.p.m Meta-chloroperoxybenzoic Acid,

percent. Hydrogen Peroxide percent Tert-butanol, percent DistilledWater, percent. Dipicolinic Acid, p.p.m

In this example, the amount of hydrogen peroxide in the sample indicatesthe degree of hydrolysis of the metachloroperoxybenzoic acid. Thegreater the amount of hydrogen peroxide in the solutions, the greaterthe hydrolysis and the less elfective is the bleaching and germicidalactivity of the meta-chloroperoxybenzoic acid solution.

essentially of a peroxybenzoic acid, said acid being free of groupswhich can be oxidized by peroxycar-boxylic acids, dissolved in a mixedsolvent consisting essentially of Water and tert-butyl alcohol, in whichthe tert-butyl alcohol is present in weight ratios relative to the waterof up to 1:1, and in amounts sufiicient to form a homogeneous solution.

2. The composition of claim 1 in which the peroxybenzoic acid is presentin amounts of from about 2% to about 12% by weight of the solution.

3. A stable, aqueous-based composition consisting essentially ofperoxybenzoic acid dissolved in a mixed solvent consisting essentiallyof water and tert-butyl alcohol, in which the tertbutyl alcohol ispresent in weight ratios relative to water of up to 1:1, and in amountssufiicicnt to form a homogeneous solution.

4. The composition of claim 3 in which the peroxybenzoic acid is presentin amounts of from about 2% to about 12% by weight.

5. A stable, aqueous-based composition consisting es- .sentially ofmeta-chloroperoxybenzoic acid dissolved in References Cited by theExaminer UNITED STATES PATENTS 3,075,921 1/1963 Brocklehurst et a1.25299 3,130,169 4/1964 Blumbergs et a1. 252-l86 3,144,297 8/1964 Kinder252-104 XR JULIUS GREENWALD, Primary Examiner.

1. A STABLE, AQUEOUS BASED COMPOSITION WHICH CONSISTS ESSENTIALLY OF APEROXYBENZOIC ACID, SAID ACID BEING FREE OF GROUPS WHICH CAN BE OXIDIZEDBY PEROXYCARBOXYLIC ACIDS, DISSOLVED IN A MIXED SOLVENT CONSISTINGESSENTIALLY OF WATER AND TERT-BUTYL ALCOHOL, IN WHICH THE TERT-BUTYLALCOHOL IS PRESENT IN WEIGHT RATIOS RELATIVE TO THE WATER OF UP TO 1:1,AND IN AMOUNTS SUFFICIENT TO FORM A HOMOGENEOUS SOLUTION.